Applying a projection pursuit model for evaluation of ecological quality in Jiangxi Province, China

Monitoring and evaluating ecological quality and changes are crucial for policy formulation to guide ecosystem management and socioeconomic sustainable development. However, evaluation of ecological quality is still very challenging due to difficulties in determination of its associated indicators and weights. This paper proposes supporting, providing and regulating ecosystems services-based indicators to describe ecological quality, and applies a Projection Pursuit Model to eliminate redundant indicators and objectively determine weights for an ecological quality index (EQI) on a regional scale. Taking Jiangxi Province, China, as a demonstration area, the data for indicator measures were retrieved from satellite remote sensing and ecosystem modelling with a spatial resolution of 1 km for the three years 2005, 2010 and 2015. The results suggest that Normalized Difference Vegetation Index (NDVI) and water use efficiency (WUE) should be weighed higher and leaf area index (LAI) and Bowen ratio should be weighed lowest in the calculation of an EQI for Jiangxi Province. For 2015, the regional EQI was calculated to be 55.32 on a scale from 0 as the worst to 100 as the best, with higher values ascribed to the hills and mountains and the lower values existing near urban areas. The EQI increased from 52.26 in 2005 to 55.32 in 2015 with an increased area of good-and-above grade from 25.47% to 36.8% for the whole province. The changes in EQI could be attributed to a warmer and wetter climate trend playing a positive dominant effect, while urbanization and afforestation have negative and positive effects, respectively. This study demonstrates that it is feasible to evaluate ecological quality based on a comprehensive set of indicators and PPM-based weight determination, which could be further applied in regular ecological quality monitoring and evaluation on the regional, or even the national scale.